The present invention relates to a hub and brake rotor assembly for a vehicle wheel, of a type including a so-called first generation hub and bearing unit and a brake rotor, such as a disc or a drum, connected to the hub so as to be rotatable therewith, as specified in claim 1.
An assembly of the type indicated above is described in U.S. patent application published under No. US 2002/0015545 A1, from which FIG. 1 of the appended drawings was extracted.
In the description and in the claims which follow, terms such as xe2x80x9cinnerxe2x80x9d or xe2x80x9couterxe2x80x9d, xe2x80x9caxialxe2x80x9d or xe2x80x9cradialxe2x80x9d should be understood as referring to the condition fitted onto a motor vehicle.
With reference to FIG. 1, a first-generation hub and bearing unit for a vehicle wheel assembly includes a radially outer annular hub 10 and a bearing 11. The hub 10 has an outer radial flange 12, with a plurality of axial holes 13 formed therein for fixing a wheel to a vehicle, and an axial cylindrical seat with the bearing 11 mounted therein.
The bearing 11 includes two rings of rolling elements 15a and 15b, in this example taper rollers, interposed radially between a pair of radially inner rings or half-rings 16a and 16b and a radially outer ring 17. The non-rotating inner rings 16a and 16b of the bearing 11 are locked against rotation onto the wheel shaft (not shown), while the outer ring 17 is housed in the cylindrical seat 14 in the hub for rotation therewith. The seat 14 extends between two radial surfaces 18 and 19, facing inwardly and outwardly of the vehicle respectively.
The outer ring 17 of the bearing 11 includes a main, central annular portion 20 in which the raceways for the rolling elements 15a and 15b are formed. The outer ring 17 has an outer cylindrical surface 21 for fitting into the cylindrical seat 14 in the hub 10. The dimensions of the cylindrical seat 14 and the cylindrical surface 21 are such that a certain amount of radial interference is involved, requiring the bearing to be force-fitted into the hub, and thereby improving the axial and circumferential locking of the outer ring of the bearing in the hub.
The outer cylindrical surface 21 extends over the entire axial dimension of the outer ring 17 and the axial width thereof is greater than that of the seat 14. The two axially opposite ends of the main, central portion 20 of the outer ring 17 have respective annular formations 22 and 23, formed by cold deformation, usually by rolling, in such a way that they project axially beyond the lateral surfaces 18 and 19 of the annular hub 10 and can be bent radially outwards against these opposite lateral surfaces in order to lock the ring 17 to the hub 10.
In an alternative embodiment of a hub and bearing unit described in the aforesaid U.S. patent application, the outer ring 17 of the bearing 11 has only one tubular projection 22 which extends axially on the axially inward side of the ring, while the axially outward side has an axial shoulder bearing against the lateral surface 19 of the hub.
According to this prior art, a brake rotor (not shown in FIG. 1) is fitted on the hub 10 by bolts screwed into axial threaded holes 24 in the hub 10.
The present invention also relates to a hub and brake rotor assembly in which the brake rotor is coupled to the hub by cold-deformation, by rolling for example. An assembly of this type is described in European Patent EP-B-0 783 980, from which FIG. 2 of the appended drawings was extracted.
With reference to FIG. 2, in which components or elements identical or similar to those of FIG. 1 have been given the same reference numerals, a hub and bearing assembly of the so-called second generation type includes an annular hub 10 with an external radial flange 12 with axial holes 13 for fixing a wheel 25 to the vehicle.
A brake rotor 26, such as a disc or a drum, has an inner radial flange 27, arranged in the same radial plane as the flange 12 of the hub 10 so as to be fixed directly to the periphery thereof. The brake rotor 26 is coupled for rotation with the hub 10 by radial interference between the two external cylindrical surfaces 12a and 27a on the radial flanges 12 and 27 respectively of the two elements, and is locked axially on the hub 10 between a shoulder 28 and a rolled edge 29, formed at the axially outward and inward ends respectively of the surface 12a of the hub.
Equivalent embodiments (which are not illustrated here since they are easy to work out from the above description with reference to FIG. 2) provide for an additional rolled edge at the axially outer end of the cylindrical surface 12a of the flange 12, instead of the shoulder 28, or for the edge or edges to be rolled not on the hub flange 12 but on the flange 27 of the brake rotor. Furthermore, in order to improve the coupling between the hub 10 and the rotor 26, another proposal is for a toothed coupling to be formed between the cylindrical surfaces 12a and 27a of the two elements.
The object of the invention is to provide a hub and brake rotor assembly which improves on the prior art, which can be manufactured at a lower cost, which is easy and rapid to assemble and which ensures improved and more reliable operation.
This object is fully achieved by providing a hub and brake rotor assembly as defined in claim 1.